Electric discharge device comprising an activated cold cathode



Oct 1963 c. A. M. VAN DEN BROEK ELECTRIC DISCHARGE DEVICE COMPRISING AN ACTIVATED cow CATHODE Filed Feb. 5, 1961 FIG.1

FIG.2

INVENTOR CORNE LIS A M.VAN DEN BROEK YALBEW'I'US VENEMA AG EN United States Patent ice 3,105,917 ELECTREC DISCHARGE DEVICE COMPRISING AN ACTiVATED COLD CATHODE Cornelis Arnoldus Maria van den Brook and Albertns Venema, Eindhoven, Netherlands, assignors to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed Feb. 3, 1961, Ser. No. 86,985 Claims priority, application Netherlands Feb. 11, 1960 4 Claims. (Cl. 313-217) This invention relates to a gas-filled, electric discharge device comprising an activated cold cathode, which consists of a high-melting-point metal rod on which a few turns of metal wire are wound.

Electric discharge devices of the kind set forth may be used, for example, as electronic flashlight lamps. The barium-containing activating material is applied to the cathode in the form of a barium salts containing paste prior to the sealing-in of the electrodes. When the electrodes are heated during the exhaust of the tube, the barium salts are dissociated into barium oxide. The discharge may readily damage the barium oxide layer on the cathode, which may also occur already during the dissociation of the barium salts. Moreover, the material emanating from the cathode may readily give rise to blackening of the bulb, so that the luminous output is adversely affected. The activating material of the cathode impinging on the bulb wall may give rise to cracking of the glass.

The invention has for its object to provide a structure, which has advantages as compared with the known devices.

In accordance with the invention in a gas-filled, electric discharge device comprising an activated cold cathode consisting of a high-melting-point metal rod on which a few turns of metal wire are wound, the wound wire consists of sheathed wire having a core of an alkalior alkaline-earth metal alloy or of a compound of such a metal mixed with a reducing material, While on the side facing the metal rod the sheath of the wound wire is ground away to an extent such that the core engages the metal rod.

The invention may be particularly applied to electronic flashlight lamps in which the gas pressure is a few tens of centimetres of rare gas and in which the sheathed wire wound on the cathode rod consists of an iron sheath and a core of a barium-aluminium alloy, BaAl which wire is ground off down to about half the diameter.

The invention will now be described more fully with reference to the accompanying drawing, in which:

FIG. 1 shows an electronic flashlight lamp according to the invention and,

FIG. 2 shows one of the electrodes on an enlarged scale.

Referring to FIG. 1, reference numeral 1 designates an U-shaped glass bulb, in which at the ends two tungsten rods 2 are sealed. On each end of the tungsten rods a few turns of sheathed wire 3 are wound. On the outer 3,105,917 Patented Oct. 1, 1963 side of the bulb provision is'made of a conductive strip 4, which may serve as an ignition electrode.

In FIG. 2 it is'illustrated that'the sheathed wire 3 consists of a sheath 5 of a diameter of 0.8 mm. and a thickness of 0.15 mm. of iron, the core 6 consists of BaAl The sheathed wire is shown in a sectional view. The tungsten rod 2 also has a diameter of 0.8 mm. The sheathed wire 3 is ground off down to half the diameter, although this measure is not critical; a smaller depth of grinding may also sufiice.

The electronic flashlight lamp filled with xenon of a pressure of 30 cms. Hg was used experimentally inter alia the lamp Was ignited 10,000 times at a frequency of 8 per minute and an energy quantity of w./sec. per flash. No blackening could be observed on the glass and the ignition voltage of the tube had not increased. If desired, the other electrode may be connected as the cathode after long use.

What is claimed is:

1. A gas filled electric discharge device including an activated cold cathode comprising a rod of a high melting point metal, a plurality of turns of wire wound on said rod, said wire comprising a core consisting of a material containing a metal selected from the group consisting of alkali metals and alkaline earth metals, said material being reducible to one of said metals, from said group and an iron sheath surrounding said core except for a portion of the core which engages the rod.

2. A gas filled electric dischargedevice including an activated cold cathode comprising a rod of a high melting point metal, a plurality of turns of wire wound on said rod, said wire comprising a core consisting of an alloy of a metal selected from the group consisting of alkali metals and alkaline earth metals, said alloy being reducible to one of said metals from said group, and an iron sheath surrounding said core except for a portion of the core which engages the rod.

3. A gas filled electric discharge device including an activated cold cathode comprising a rod of a high melting point metal, a plurality of turns of wire wound on said rod, said wire comprising a core consisting of a barium-aluminium alloy, and an iron sheath surrounding said core except for a portion of the core which engages the rod.

4. A gas filled electric discharge device including an envelope, a rare gas filling in said envelope, and an activated cold cathode comprising a tungsten rod, a plurality of turns of wire wound on said rod, said wire comprising a core consisting of BaAl and an iron sheath surrounding said core except for a portion of the core which engages the rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,147,447 Kolligs Feb. 14, 1939 2,175,345 Gaidies Oct. 10, 1939 2,499,192 Laiferty Feb. 28, 1950 2,504,581 Power Apr. 18, 1950 

1. A GAS FILLED ELECTRIC DISCHARGE DEVICE INCLUDING AN ACTIVATED COLD CATHODE COMPRISING A ROD OF A HIGH MELTING POINT METAL, A PLURALITY OF TURNS OF WIRE WOUND ON SAID ROD, SAID WIRE COMPRISING A CORE CONSISTING OF A MATERIAL CONTAINING A METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS, SAID MATERIAL BEING REDUCIBLE TO ONE OF SAID METALS, FROM SAID GROUP AND AN IRON SHEATH SURROUNDING SAID CORE EXCEPT FOR A PORTION OF THE CORE WHICH ENGAGES THE ROD. 